The invention comprises a process for preparing alkylene diisocyanates by heating N,N'-alkylene urea-N,N'-dicarbonyl chlorides at a temperature sufficient to cause dephosgenation.
Aliphatic diisocyanates have generally been prepared by an azide degradation process known as the Curtius method. Tilley et al. in U.S. Pat. No. 3,275,618 (1966) describe the preparation of alkylene diisocyanates by pyrolysis of N,N'-alkylene allophanyl chlorides.